Photoreception is a ubiquitous sensory ability found across the Metazoa, and photoreceptive organs are intricate and diverse in their structure. Although the morphology of the compound eye in Drosophila and the single-chambered eye in vertebrates have elaborated independently, the amount of conservation within the ‘eye’ gene regulatory network remains controversial, with few taxa studied. To better understand the evolution of photoreceptive organs, we established the cephalopod Doryteuthis pealeii as a lophotrochozoan model for eye development. Utilizing histological, transcriptomic and molecular assays, we characterize eye formation in Doryteuthis pealeii. Through lineage tracing and gene expression analyses, we demonstrate that cells expressing Pax and Six genes incorporate into the lens, cornea and iris, and the eye placode is the sole source of retinal tissue. Functional assays demonstrate that Notch signaling is required for photoreceptor cell differentiation and retinal organization. This comparative approach places the canon of eye research in traditional models into perspective, highlighting complexity as a result of both conserved and convergent mechanisms.
The authors declare no competing or financial interests.
Conceived of project: K.M.K., J.M.G. Designed experiments: K.M.K., J.M.G. Executed experiments: K.M.K., P.S. Analyzed data: K.M.K., J.M.G., E.M. Wrote manuscript: K.M.K. Edited manuscript: K.M.K., J.M.G.
This work was funded by a fellowship from the Grass Foundation to K.M.K.; a Plum Foundation Research Award; a H. Keffer Hartline and Edward MacNichol, Jr. Fellowship Award; a Laura and Arthur Colwin Endowed Summer Research Fellowship Fund Award; and a National Science Foundation CAREER Award [IOS-0745782 to J.M.G.].
All raw reads and annotated data have been deposited at the NCBI (http://www.ncbi.nlm.nih.gov/sra; SRA accession numbers SRP065414 and SRP066528).
Supplementary information available online at http://dev.biologists.org/lookup/doi/10.1242/dev.134254.supplemental
- Received December 22, 2015.
- Accepted July 25, 2016.